This invention relates to pole type structural support members and particularly to a pole construction which may be used to support electrical transmission lines and related components either singly or by combining several to form a frame or lattice. Also, this invention relates to the method of forming such a pole construction. Pole structures commonly used for supporting transmission lines are either wood, pre-stressed concrete, or hollow tubular steel. Structural steel or aluminum are commonly used for constructing frames and lattices. As to poles, the hollow tapered steel construction has widespread use. Such poles are usually formed by bending steel sheets or plates on a press brake to form two half sections which would then be seam welded to produce sections of the pole. The various sections would then be butt welded to each other to form the tapered pole. Another method of constructing tapered steel poles is to shape the individual sections such that a larger section would slip into the end of a smaller section and be pressed at the overlap to secure the sections together to form the pole.
Regardless of which method is used to form tapered steel poles, each has the inherent problem of being expensive to produce mainly because of the complex costly equipment required for their production. The steel sheet or plate must be cut to shape, pressed into rounded or near rounded shapes and then seam and butt welded as described above. Each stage of production requires its own particular piece of equipment with each operation being time consuming and thus expensive. In addition to the expense, obtaining good, strong butt welds is always a major problem. It is vital to obtain a welded joint having the full tensile strength of the pole section. Because of the difficulty of obtaining high strength welds, high strength steel sheet or plate cannot always be used.
This invention overcomes the problems inherent in producing tapered poles by providing a pole construction formed of inexpensively produced straight tubular sections which are joined withoug welding to form a pole of progressively decreasing outer diameter. The pole construction of this invention has strong nonwelded joints, resists both axial tension and compression loads as well bending moments imparted to the overall structure, and may be constructed without the need of high-priced complex equipment.